Telephone intercept circuit



Oct. 5, 1954 T. FRANKEL TELEPHONE INTERCEPT CIRCUIT 4 Sheets-Sheet 1 Filed April 14, 1951 Tv F d o2 ci i lrT l l li INVENTOR.

THEODOR FRANKEL BY ATTORNEY illll KOHUMZZOQ ol. C 0 o oooo q 0|) mtb [IL 'Oct. 5, 1954 T. FRANKEL 2,691,069

TELEPHONE INTERCEPT CIRCUIT Filed April 14, 1951 4 Sheets-Sheet 2 CONNECTOR o l L C INTERCEPT LINE CCT.

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TELEPHONE INTERCEP' CIRCUIT Filed April 14, 1951 4 Sheets-Sheet 5 TRUNK CCT.

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THEODOR FRANKEL BY ffm ATTORNEY Oct. 5, 1954 T. FRANKEL TELEPHONE INTERCEPT CIRCUIT 4 Sheets-Sheet 4 Filed April 14, 1951 INVENTOR.

ATTORNEY Patented Oct. 5, 1954 UNITED STATES site TENT GFFECE TELEPHONE INTERCEPT CHR'CUIT Theodor Frankel, Rochester, N. Y., assigner to Stromberg-Carlson Company, a corporation of New York 4 Claims.

This invention relates to automatic telephone systems and more particularly to intercept means for automatic telephone systems.

Intercept circuits have been proposed hereto fore in which calls to be intercepted are routed to an intercept operator by means of a plurality of intercept line circuits and an intercept trunk. For an example of a suitable circuit of this type see the co-pending application of Frank Kessler, Serial No. 37,458, filed July '7, 1948, now Patent 2,595,362, and assigned to the same assignee as the present invention.

in an automatic telephone exchange, it often is necessary to intercept calls which are directed to unused terminals of an automatic switch. These terminals may bc vacant either because a subscriber has been disconnected or because portions of the switch are unused so that room may be left for expansion as the exchange grows. Usually calls to these unused terminals are eX- tended to an operator position. The operator then either attempts to complete the call or explains to the calling subscriber why the call cannot be completed. One type of calls which may be directed to the intercept operator is a toll call which was originated by and extended from a distant exchange. In toll calls of this type, a distant opera-tor merely dials the number of the local called subscriber after which she directs her attention to another call. Some recall means mus-t be provided in case this toll call is intercepted, otherwise the attention of the distant operator would not again be directed to this particular call and therefore that operator would thinl; that it was completed in the usual manner. This recall feature is commonly known as answering supervision. Ordinary local. calls may also be intercepted. These local calls conventionally are from various types of subscribers, including pay stations. The pay station telephone ordinarily collects a coin on receipt of answering supervision.

It, therefore, becomes necessary for an intercept operator to return answering supervision to the distant toll operator butl not to a local subscriber. In the past, the intercept operator has rst received a call, second determined the origin of the call and third operated various keys selectively to control the transmission or answering supervision dirlerentiy in accordance with the nature of the calling party. This procedure is undesirable since it requires extra training for an intercept operator and since it sometimes leads to undesired collection ci coins. Therefore, it is desirable to provide an automatic arrangement by which the origin oi the call may be determined and by which answering supervision either will or will not be returned without requiring any extra thought process on the part of the operator.

It is, therefore, an object of this invention to provide new and improved intercept trunk. means.

Another object of my present invention is to provide an intercept trunk which has means for distinguishing between local and toll calls.

Still another object of the present invention is to provide an intercept circuit capable of dis tinguishing between local and toll calls and to provide answering supervision only in connection with toll calls.

The foregoing objects of my invention are achieved in the preferred embodiment of my invention by making use of a toll line relay in the connector as part of monitor means for distinguishing between local and toll calls reaching an intercept trunk. In order to provide the necessary distinction between toll and vlocal calls, I provide a series circuit including a resistor shunted by a pair of normally open relay contacts (the contacts being under the control of the toll line relay), a control conductor extending beltween the connector and the intercept trunk circuit and two relays in the trunk circuit. The first of the two trunk relays is chosen to be operated by current flowing in the above-mentioned series circuit including the resistor but the second trunk relay is of the marginal type and is not energized by the resistance current. On toll calls, operation of the toll line relay is employed to cause snorting of the resistor by closing the normally open contacts shunting the resistor. The resulting increase of current in the abovementioned series circuit is of such value as to operate the second trunk relay. In order to permit the intercept operator to provide answering supervision only on toll calls, there is provided an impedance which is arranged to be connected across the extended talking conductorsthrcugh normally open contacts of the second trunk relay. Hence, on local calls, the second trunk relay is not operated and the loop is not completed through the impedance because the circuit across the loop is broken at the normally open contacts associated with the second trunk relay. On toll calls, however, the normally open contacts asso elated with the second trunk relay are closed and thereby the loop across the extended talking conductors is closed and answering supervision may be provided by the intercept operator.

The features of my invention which I believe to be novel are set forth with particularity in the appended claims. My invention, both as to its organization and manner of operation, together withfurther objects and advantages thereof may best be understood by reference to the following description taken in connection with the accom` panying drawingsI in which Figs. l, 2, 3 and 4 when placed as shown in Fig. 5 illustrate an automatic telephone system having intercept facilities embodying the principles of my invention.

In order to simplify the illustrations and to facilitate the explanation of the operation of the circuits shown in the drawings, certain parts of the telephone system and circuits constituting the present embodiment of my invention have been shown diagrammatically and certain con ventional illustrations have been' employed, the drawings having been made more with the purpose of making it easy to, understand the principles and mode of operation than with the idea of illustrating the specific construction and arrangement of parts that would be actually employed in practice. For example, the various relays and their contacts are illustrated in a conventional manner with all of the contacts controlled by a particular relay being associated with this relay by means of a vertical dashed line. The nder and selector switches for associating a calling line with an intercept circuit are illustrated in block form, as shown in the left hand portion of Fig. 1. Only a portion of the connector circuit is illustrated in Fig, l. The negative side of the common exchange battery or source of potential is indicated by andthe positive side of the exchange battery, which is usually grounded', is indicated by (-l-). For convenience in illustrating and describing the features of the present invention, it is assumed that the invention is applied to a party line telephone system of the harmonic ringing type.

Referring to the drawings, there is shown in Fig. l a local subscriber indicated' by the letter A, the local subscriber A being represented by the simulated dial There is shown a plurality vof leads or conductors extending between the substationA and the terminals of a line finder. These may be identied as the talking conductors T and R or in other language the tip and ring leads. There is also provided a sleeve lead S extending between the connector multiple and the line ilnder bank for purposes well known in the art. A control lead HS is also illustrated. The schematic representation of' the line nder indicates a plurality of sets of terminals with four brushes.

It is to be understood that in a manner well understood in the art, upon the appearance of `a calling condition on the line extending to substation A, the line finder is set in operation to nd the calling line and thereby connect the calling line to the rst selector. As is well understood in the art, the operation of dial I may be employed to extend the call through the automatic step switch associated with selector S in order to extend the talking conductors to the connector shown on the right hand portion of Fig. 1 in skeleton form. It may be noted that the selector comprises four sets of contacts and illustrates the provision of four brushes.

Referring to the right hand portion of Fig. l there is illustrated the presence of a calling bridge relay |30, answering bridge relay |40, ring trip relay |50 and cut through relay |60 (Fig. 2) which operate in conventional manner under the control of the dial to extend a call from substation A to a desired called line.

It is now assumed that the called line is on intercept either because a private line is to be intercepted or because one subscriber on a party line is to have intercept service. In Fig. 2 there is shown a plurality of intercept line circuits. The party lines are provided with a harmonic ringing system as illustrated in Fig. l wherein a minor switch constitutes the party selecting device. Assuming a call to a party line, the minor switch is advanced upon the dialing of a ringing digit in order to select and apply to the ring lead R the proper ringing frequency as by means of the left wiper and bank of the minor switch. When a subscriber has dialed an intercepted Vnumber he is connected to the intercept circuit shown in Fig. 2 through the cross-connections indicated by the letters a, b, c and d in Fig. 2. The ringing current is connected through the left wiper and bank of the minor switch, the upper winding of ring tripzrelay |50, rest contacts |55, operated contacts on relay |50, ring conductor R, strap c, the winding of alternating current relay 220, capacitor C2, resistor R2, strap b, tip conductor T, operated contacts on relay |60, to ground on contacts iI, thereby operating the relay 220. If it is assumed that the intercepted number is connected to the first line in the group of Fig. 2, the intercept line relay Zit is operated over a circuit extending from battery through the upper winding of relay 2|0, operated contacts 22| of relay 220, normal contacts 2| ci relay 2 l0, a chain of normal contacts of the other line relays including the last line relay 2|0a in the group to ground.

With this arrangement it is to be noted that if two intercepted numbers are dialed by different subscribers and two lines in the group are sirnultaneously seized, only the first line will be connected as all other lines are required to go through a chain of contacts of relays 22B-220e.

Relay 2|0 is held operated over a circuit extending from battery through the lower winding of relay 2|0, operated contacts 2|2 and control conductor HG| extending between the intercept line circuit and the trunk circuit of Fig, 3, winding of relay 330, normally closed or break contacts 34| of relay 34d, and normal contacts 42| of relay 420 to ground. Upon the completion of this circuit, relay 330 operates.

Upon the operation of line intercept relay 2|0 a circuit is completed for the operation of relay 3|i (hereinafter identied as the first trunk relay), the energizing circuit extending from ground on lead MG (upper portion of Fig. 2), make contacts 2|fi of relay 2|l, cross connector a, conductor the right hand section of the minor switch, resistor R|, operated contacts |6| of cut through relay |60, connector brush CHS, conductor HS, cross-connector d, make contacts 2|3, control conductor HS, the winding of the first trunk relay 3|0, and the winding of relay 320 (hereinafter iden'tiiied as the second trunk relay) to battery. As described hereinafter, the windings of relays 3 i 0 and 32% are chosen so that relay 3I0 operates to close its spring contacts upon the foregoing series circuit including resistor Ri, but relay 320 is of the marginal type and is not operated on the amount of current owing with re' sistor Rl in circuit, although upon the closure of the normally open contacts i2| shunting resistor RI, sufficient current ows in the foregoing series circuit to operate relay 320 in series with relay 8 The operation of relay 3|0 forwards a ground from operated contacts 3|| of relay 3|!) through .normal contacts 43| of relay 530 to lead HGr-2 extending to the intercept operators position or intercept answering trunk indicated at the right hand side of Fig. For a suitable intercept answering trunk see the above-identified Kessler application.

If the night service relay 438 is operated (as hereinafter explained) the foregoing ground is forwarded through operated contacts 1132 to lead HG-t to the intercept answering trunk or intercept operators position.

Referring baclr to the operation of relay 330, the interrupter circuit is energized by applying ground to the interrupter start lead INT START by way of operated contacts 3.3i. Operation of relay 330 also completes a circuit for energizing relay 3S@ over a circuit extending from battery through the winding of relay 360, normal contacts Ill l operated contacts 332, and normal contactsl Sll and 452i to groi'ind. In response to the operation of relay litt, relay 35@ operates over a circuit extending from battery through the winding of relay 35d and operated contacts 36! to ground. The operation of relay 339 also results in the lighting of monitor lamp MON over an obvious circuit including operated contacts 334 and normal contacts i i 2.

The succeeding circuit, in this case the intercept answering trunlr under the control of the intercept operator, answers the intercepted call by placing a ground on lead Sl in a manner well known in the art.

In response to the appearance of ground on lead Si, relay dit operates over a circuit extending from battery through the upper winding of relay MS, operated contacts 35i and conductor or lead Si to the intercept answering trunk. Relay dit locks through its own operated contacts ll l i to ground on the Si lead.

The tip lead T is extended through operated contacts 215, 352 and All t to resistance ground, the lower winding of relay 430 being employed as a resistance, and the ring lead R is extended to resistance ground through operated contacts 2W, 353 and Mil to resistance ground, the lower winding of relay lill constituting the necessary resistance. Ring trip relay i563 in the connector shown in Fig. l operates over its upper winding and locks through its lower winding to the connector master ground Via its f or preliminarily operated contacts 53 but answering bridge relay Idil is not operated and the alternating current relay 22e releases because of the removal of the energizing ringing frequency. Therefore, no change is made in the marking extended through contacts M2 and the lower winding of relay lli) to the lowerinost brush of the irst selector; hence no answer supervision is returned.

Referring again to the operation of relay IMQ, a circuit is provided through operated contacts i5 for operating relay 42d over an obvious circuit and the operation oi relay lill releases relays 35d and 35i! by opening contacts il l.

The foregoing description relates to the extension of a call from a local calling line to an intercept answering trunk. There is now described the arrangement for extending an intercepting call from a calling toll line. A calling toll line is indicated in the left-hand portion of Fig. l by the legend Distant Toll Operator. In a manner well understood in the art, the toll operator applies battery to the HS lead as by means of a suitable key K and the nder selector link operates to iind the calling line and extends the calling toll line to the connector thereby energizing toll line relay l ill over the HS lead in an obvious manner. The operation of relay Il causes energization of auxiliary toll relay |20 over a circuit including operated contacts ill and normal contacts 122. Upon the operation of relay |20, contacts l2! are closed to short out resistor RI.

A circuit is now completed for operating relay 32!! in the trunk circuit over a series circuit extending from battery at relay 32E) through the windings of relays 32B and SIB in series, the HS lead, operated contacts 2I3, connector d, brush and contacts CHS, operated contacts ll and i2l, the right-hand minor switch section, jumper a, and operated contacts 2id to ground. Since resistor Ri is now cut out of the series circuit, relay 324] receives enough current to operate that relay. In this manner, means is provided for discriminating between local and toll calls. In other words, on local calls relay 3m operates but relay 320 does not. On the other hand, on toll calls both relays 3m and 32@ operate. The resulting operation of the trunk circuit is the same as pre viously described up to the time that the talking conductors T and R are extended to the intercept answering trunk. On a toll call, the intercept operator can give answering supervision in the following manner. For this purpose there is provided a ila-Shing relay 470. If the wiring indicated by the letter U is used, dashing by ringing on the trunk is provided. With this arrangement, the alternating current ringing current enters on tip lead T and is conducted through the upper winding oi relay ille, condenser Cfl and resistance R13 to the ring lead R, thereby operating relay 410. If the V wiring is used, means is provided for operating relay lllil by connecting battery to either tip lead T or ring lead R. If battery is applied to tip lead T, it is conducted through the upper winding of relay -ilii to ground on the V wiring. If battery is applied to ring lead R, it is conducted through the lower winding of relay lill to ground on the V wiring.

In response to the operation of relay dit, relay 48B is operated over a circuit extending from battery through the winding of relay fide, operated contacts dll, M6 and 332, and normal contacts 3M and 327i to ground. The operation of relay @Sil completes a circuit for energizing relay 4553, that circuit extending from battery through the winding of relay 45t, normal contacts 449, operated contacts it! of relay liti), make contacts dit and 332 and normal contacts 313i and @2l to ground. Operation of relay 5Fl e-nergizes relay 4t from battery through relay 550, operated contacts liili, winding of relay dt, operated contacts el@ and 332, normal contacts 3M and operated contacts dit) to ground. When relay lll is released by the intercept operator, relay itil releases because of the opening of contacts lill. Upon the release of relay e613, the energization circuit for relay 35e is ope-ned at contacts 156i but relay 45B remains operated through contacts 45E and relay M0.

Impedance coil RE is now connected between the calling tip and ring leads T and R, respectively, the circuit extending from the R lead through operated contacts Mil, left-hand winding of impedance RE, operated contacts 32H, righthand winding of impedance RE, and normal contacts 1362 to tip lead T, thereby completing the loop across the tip and ring leads and resulting in the operation of the answering bridge relay fl shown in the connector of Fig. 1 to give answering supervision by any well known means, such as by closing contacts MI to transmit a battery marking to the lowermost wiper of the rst selector, for example.

The tol-1 operator and the intercept operator are now connected on a talking basis.

Night service may be given by placing a ground on lead NS. This ground is forwarded through normal contact M9 of relay fil() to relay 43d, and relay 4,3 locks to ground on the NS lead through its own operated contacts 433.

If a number on a party line is dialed which has not been intercepted but another number on that same party line has been intercepted, an intercept line circuit of Fig. 2 is seized and the proper intercept relay, for example, relay 250, and alternating current responsive relay, for example, relay 226, operated. In turn the relay 333 inthe trunk circuit (Fig. 3) is operated as previously described. In this case, however, relay SIB is not operated because the minor switch comes to rest on a contact which is not jumpered to ground as by means or a strap a and, hence, no ground is furnished to operate relays 3 i 0 and 32d.

When the calling party releases, relay 3&0 is released if the number dialed was one number of a party line because of the return of the nder switch to itshome or normal position.

It will be recalled that the operation of relay 33e started the interrupting machine by closing contact 33|. A momentary ground is forwarded on the pickup lead PU by way of normal contacts BIS and operated contacts 333 to momentarily operate relay 3MB which holds open the holding path of relay 33) and the intercept line relay at now open contacts 34|. As a result relays 330 and 2m are released. When the succeeding circuit releases, ground is removed from lead Si which releases relay dit'. In turn, relay 620 is released at now open contacts H5 and the release of relay lill also removes the holding ground for relays 1140 and 456 at now open contacts 4I6.

From the foregoing description it is seen that there is provided a discriminating circuit according to which rst trunk relay 3H] operates on both toll and local calls but second trunk relay 320 operates only on toll calls and the talking loop is extended and answering supervision is permitted by enabling the talking loop to be completed through impedance RE and contacts 32 of relay 32E? only in response to the extension of toll calls to the trunk circuit.

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that changes and modiiications may be made without departing from my invention in its broader aspects. I, therefore, aim in the appended claims to cover all such changes and modiiications as fall within the true spirit and scope of my invention.

What is claimed is:

l. In a telephone system having a plurality of toll lines, a toll operators position for extending calls from said toll lines, a plurality of local lines, each of said lines having a pair of talking conductors, an intercept trunk circuit, iirst and second trunk relays, means for operatively connecting said relays into said trunk circuit, an intercept operators position, and means for extending the talking conductors o1" a calling line through said intercept trunk circuit to said intercept operators position responsive to a call from one of said lines to an intercepted subscriber on one oi said lines, means for distinguishing between local and toll calls comprising means for operating only said iirst trunk relay on local calls and for operating both of said trunk relays on toll calls, and means responsive only to the operation of said second trunk relay for closing a loop across the extended talking conductors, means to return answering supervision to said toll operators position only on toll calls, and means whereby said last-named means is made eiective responsive to the closing of said loop across said talking conductors.

2. In a telephone system having a plurality of toll lines, a toll operators position for extending calls from said toll lines, a plurality of local lines, each of said lines having a pair of talking conductors, an intercept trunk circuit having rst and second trunk relays, means for operatively connecting said relays into said trunk circuit, contact means operated by each of said trunk relays, an intercept operators position, and means for extending the talking conductors of a calling line through said intercept trunk circuit to said intercept operators position. responsive to a call from one of said lines to an intercepted subscriber on one of said lines, means for distinguishing between local and toll calls comprising means for operating only said first trunk relay on local calls and for operating both of said trunk relays on toll calls, an impedance, means responsive only to the operation of said second trunk relay for closing a loop including said impedance across the extended talking conductors, means to return answering supervision to said toll operators position only on toll calls, and means whereby said last-named means is made eiective responsive to the closing of said loop across said talking conductors.

3. In a telephone system having a plurality of toll lines, a toll operators position for extending calls from said ltoll lines, a plurality of local lines, each of said lines having at least a pair of talking conductors, an intercept trunk circuit, a first trunk relay having characteristics such that it operates responsive to wide margins of operating potentials, a second trunk relay having characteristics such that it operates on a narrow margin of operating potentials, first circuit means operatively connecting each of said relays into said intercept trunk circuit, an intercept operator position, means for extending the talking conductors of a calling line through said intercept trunk circuit to said intercept operator position responsive to a call from said calling line to another of said lines which is connected for intercept service, a control relay, contacts operated to either of two positions by said control relay, second circuit means operatively connecting said control relay to be controlled over said calling line, a resistor, means including said set of contacts for switching said resistor into and out of said iirst circuit, means for distinguishing between a rst class oi calls over said local lines and a second class of calls over said toll lines comprising means for selectively operating said control relay only on calls of one of said classes, said wide margin trunk relay operating when said control relay contacts are in both of its said positions, said narrow margin trunk relay operating only when said control relay contacts are in one of its said positions, means responsive to the operation of one of said trunk relays for completing a loop across said talking conductors, means to return answering supervision to said toll operators position, and means for rendering said last-named means eiective responsive to the completion of said loop; whereby, answer supervision is returned only when one of said trunk relays operates.

4. In a telephone system having a plurality of toll lines, a toll operators position for extending calls from said toll lines, a plurality of local lines, each of said lines having a pair of talking conductors, automatic switches for extending calls from either said toll lines or said local lines, station selecting means, a irst control conductor between said toll operators position and said automatic switches, means including a control relay having a pair of normally opened contacts and operative only upon the presence of a control potential on said iirst control conductor and thereby being responsive only to toll calls for closing said contacts, a resistor connected across said contacts, an intercept line circuit, connected to said automatic switches, a second control lead extending between said automatic switches and said intercept line circuit, an intercept trunk circuit having rst and second trunk relays, said rst trunkrelay having characteristics such that it operates on a rst margin of operate potentials and the second of said relays having characteristics such that it operates on a different margin of operate potentials, contact means controlled by each of said trunk relays, an intercept operators position, a source of potential, and means for extending the talking conductors of a calling line through said automatic switches, said intercept line circuit, and said intercept trunk to said intercept operators position in response to a call from one of said lines to an intercepted subscriber on one of said lines; the combination therewith of means for distinguishing between local and toll calls comprising a series circuit including said station selecting means, said relay contacts, said second control lead, windings on both of said trunk relays and said source of potential; means for closing a loop across the extended talking conductors, said loop comprising an impedance, a series circuit across said talking conductors comprising a pair of normally opened contacts of said second trunk relay and said impedance; means to return answer supervision to said toll operator only on toll calls, means for rendering said lastmamed means effective only responsive to the closing of said loop, said margin of said first trunk relay being constructed to operate in response to a call from any of said lines, said margin oi' said second trunk relay being constructed to operate only when said control relay is operated to shunt out the resistor in said series circuit whereby said second trunk relay is operative only on toll calls but is not operative on local calls whereby said loop completing circuit is completed only on toll calls in order to give answering supervision to the calling toll operator.

References Cited in the file 0f this patent UNITED STATES PATENTS Number Name Date 1,930,612 Getz Oct. 17, '1933 1,950,129 Whitney Mar. 6, 1934 2,021,286 Butz Nov. 19, 1935 2,105,898 Whitney Jan. 18, 1938 2,344,634 Powell Mar. 2l, 1944 

